1. Field of the Invention
The present invention relates to a resin seal type semiconductor device, and a method for producing the same.
2. Description of the Related Art
Recently, in keeping with the tendency toward high density packaging of electrical appliances, there has been increased demand for thin and small-sized semiconductor devices, and the production quantity of resin seal type packages such as Ball Grid Array/Chip Size Package (BGA/CSP) has increased. In these circumstances, in order to improve BGA/CSP production or the like, a production method using package molding/saw cutting techniques has been widely used where a plurality of integrated circuit (IC) chips are fixed to one wiring substrate and sealed all together by mold resin. Thereafter, the wiring substrate is cut into separate semiconductor devices.
FIG. 2 is a cross sectional view showing an example of a conventional semiconductor device.
The semiconductor device shown in this drawing is that of BGA/CSP type produced by using package molding/saw cutting technique. An IC chip 3 is fixed onto a wiring substrate 1 by an adhesive agent 2. The wiring substrate 1 is, for example, formed of a glass/epoxy substrate having a thickness of 0.2 mm or thereabouts. Wiring patterns 1a and 1b are respectively formed on face and reverse surfaces of the wiring substrate 1 in the periphery thereof and are electrically connected to each other via a through hole 1c. 
The wiring pattern 1a formed on the face surface of the wiring substrate 1 and an electrode 3a on the surface of the IC chip 3 are connected by a wire 4 such as gold wire. The surface of the wiring substrate 1 is sealed by a mold resin 5 having a predetermined thickness so as to protect the IC chip 3 and the wire 4. A soldering ball 6 having a diameter of 0.5 mm or thereabouts is attached to the wiring pattern 1b formed on the reverse surface of the wiring substrate 1 so as to make connection with a printed circuit board or the like.
Such semiconductor devices as above are produced by the following process.
First, a wiring substrate is produced in which plural sets of wiring patterns 1a and 1b, and through holes 1c are arranged, corresponding to each of the plural IC chips 3, in transverse and vertical directions in a region around a corresponding IC chip 3. Subsequently, the plural IC chips 3 are each fixed by the adhesive agent 2 to a predetermined position on the wiring substrate, and an electrode 3a on the surface of the IC chip 3 and the wiring pattern 1a corresponding thereto are connected by the wire 4 for wire bonding.
Further, the wiring substrate on which the plural IC chips 3 are mounted is placed on a lower metallic mold heated to 170xc2x0 C. or thereabouts, and a corresponding upper metallic mold is placed thereon. The mold resin 5 is injected from an injection hole formed in the upper metallic mold into an interior of the molds and a cavity formed by an inner surface of the upper metallic mold, and the wiring substrate is sealed by the mold resin 5.
After the mold resin 5 has been cured, the wiring substrate of which surface is sealed by the mold resin 5, is taken out by releasing the upper and lower metallic molds therefrom. The resin-sealed wiring substrate is cut into separate semiconductor devices corresponding to the IC chips 3 by using a cutting saw. The soldering ball 6 is attached to the wiring pattern 1b on the reverse side of each of the separate wiring substrates 1, to thereby form a complete semiconductor device. Thus, productivity markedly improves as compared with a method in which wiring semiconductor devices are separately molded one by one.
However, the above-described structure of semiconductor devices and method for producing the same, which have been conventionally known, have the following problems.
When the wiring substrate having dimensions of, for example 60 mmxc3x97180 mm, is placed on a lower metallic mold heated to 170xc2x0 C. or thereabouts, the wiring substrate is warped due to heat from the lower metallic mold and a portion of the wiring substrate may be raised from the lower metallic mold. When the upper metallic mold is placed on the wiring substrate in the above-described state, there exists a problem in which the bonded wire 4 contacts the inner surface of the upper metallic mold and thereby deforms. In this regard, there is a risk of causing short-circuits due to deformed wires 4 contacting each other.
The present invention has been devised to solve the above-described problems existing in the conventional method, and an object of the present invention is to provide a semiconductor having a structure in which reduced deformation of a bonded wire occurs, and a method for producing the semiconductor device.
In order to solve the above-described problem, in accordance with a first aspect of the present invention, there is provided a method for producing a semiconductor device, comprising the steps of: (a) bonding a plurality of semiconductor elements onto a wiring substrate, the wiring substrate having a wiring pattern formed thereon for external connection, and each semiconductor having a surface with an electrode thereon; (b) connecting the electrode on the surface of each of the semiconductor elements to the wiring pattern on the wiring substrate with a metal wire; (c) fixing a contact prevention resin having a predetermined height to the surface of at least one of the plurality of semiconductor elements; (d) placing the wiring substrate, with the surface of each of the semiconductor elements facing upward, in a lower metallic mold for mold processing; (e) putting an upper metallic mold for mold processing on the wiring substrate placed in the lower metallic mold; (f) injecting mold resin into a space formed between the wiring substrate and the upper metallic mold for sealing the semiconductor element and the metal wire on the wiring substrate; and (g) cutting the wiring substrate sealed by the mold resin into portions corresponding to the plurality of semiconductor elements to thereby form a plurality of semiconductor devices.
In the first aspect of the present invention, since the above-described method for producing a semiconductor device is provided, the following operation is performed.
A plurality of semiconductor elements are bonded onto a wiring substrate on which wiring patterns are formed corresponding to the plurality of semiconductor elements. Further, an electrode on the surface of each of the semiconductor elements and a wiring pattern corresponding thereto are connected by a metal wire and contact prevention resin having a predetermined height is fixed to the surface of each of the semiconductor elements. The wiring substrate on which the plurality of semiconductor elements are mounted, is placed on the lower metallic mold for mold processing, and an upper metallic mold is placed on the wiring substrate. The mold resin is injected into the space formed between the upper metallic mold and the wiring substrate, thereby sealing the wiring substrate. The wiring substrate sealed by the mold resin is cut into portions corresponding to the semiconductor elements, thereby forming a plurality of semiconductor devices.
In accordance with a second aspect of the present invention, there is provided a method for producing a semiconductor device, comprising the steps of: (a) bonding a plurality of semiconductor elements onto a wiring substrate, the wiring substrate having a wiring pattern for external connection formed thereon, and each semiconductor having a surface with an electrode thereon; (b) connecting the electrode on the surface of each semiconductor element to the wiring pattern on the wiring substrate with a metal wire; (c) placing, in a lower metallic mold for mold processing, the wiring substrate with the surfaces of the semiconductor elements facing upward; (d) placing an upper metallic mold for mold processing on the wiring substrate placed in the lower metallic mold, the upper mold having a contact prevention protruding portion on an internal surface of the upper metallic mold; (e) injecting mold resin into a space formed between the wiring substrate and the upper metallic mold sealing the semiconductor element and the metal wire on the wiring substrate; and (f) cutting the wiring substrate sealed by the mold resin into portions corresponding to the plurality of semiconductor elements to thereby form a plurality of semiconductor devices.
In the second aspect of the present invention, preferably, the protruding portion on the internal surface of the upper metallic mold is formed at a position corresponding substantially to the center of at least one of the plurality of semiconductor elements bonded to the wiring substrate, and a dimension of the protruding portion in a direction in which it protrudes is greater than a distance between the surface of the semiconductor element and a highest maximum position of the metal wire, and smaller than a height of the mold resin injected onto the semiconductor element, relative to surfaces of the semiconductor element.
Further, in the second aspect of the present invention, preferably, the protruding portion on the internal surface of the upper metallic mold is formed at a boundary between the semiconductor elements, and a dimension of the protruding portion in a direction to which it protrudes is equal to a height of a space formed between the wiring substrate and the upper metallic mold.
In the above-described first and second aspects of the present invention, the following operation is performed.
A plurality of semiconductor elements are bonded onto a wiring substrate on which wiring patterns are formed corresponding to the plurality of semiconductor elements. An electrode on the surface of each of the semiconductor elements and a wiring pattern corresponding thereto are connected by a metal wire. The wiring substrate on which the plurality of semiconductor elements are mounted, is placed on a lower metallic mold for mold processing. An upper metallic mold having a contact prevention protruding portion formed inside thereof, is placed on the wiring substrate. Mold resin is injected into a space formed between the upper metallic mold and the wiring substrate, thereby sealing the wiring substrate. The wiring substrate sealed by the mold resin is cut into portions corresponding to the semiconductor elements, thereby forming a plurality of semiconductor devices.
In accordance with a third aspect of the present invention, there is provided a semiconductor device comprising: (a) a semiconductor element having a plurality of electrodes on the surface thereof; (b) a wiring substrate having a wiring pattern for external connection, to which wiring substrate the semiconductor element is fixed by an adhesive agent applied to a reverse surface thereof; (c) a metal wire connecting the plurality of electrodes on the semiconductor element to the wiring pattern of the wiring substrate; (d) contact prevention resin having a predetermined height, fixed substantially at the center of the surface of the semiconductor element; and (e) mold resin sealing and protecting the surface of the wiring substrate, the semiconductor element, the metal wire, and the contact prevention resin.
According to the first aspect of the present invention, the contact prevention resin having a predetermined height is adhered to the surface of each of the semiconductor elements. As a result, even if the wiring substrate warps due to heating or the like, when the upper metallic mold for mold processing is placed on the wiring substrate, the inner surface of the upper metallic mold abuts against the contact prevention resin, and thus the metal wire is protected. Therefore, there is reduced risk of deforming the metal wire.
According to the second aspect of the present invention, the contact prevention protruding portion is formed at the inner side of the upper metallic mold for mold processing. As a result, even if the wiring substrate warps, the metal wire is protected by the protruding portion of the upper metallic mold when the upper metallic mold is placed on the wiring substrate. Accordingly, there is reduced risk of deforming the metal wire.
Further, in the second aspect of the present invention, the protruding portion provided inside of the upper metallic mold is preferably formed at a position corresponding substantially to the center of the semiconductor element bonded onto the wiring substrate in such a manner that the dimension of the protruding portion in a direction to which it protrudes is greater than a distance between the surface of the semiconductor element and the highest position of the metal wire connected to the semiconductor element, and is also smaller than the height of the mold resin injected onto the semiconductor element from the semiconductor element surface. As a result, even if the wiring substrate warps, the protruding portion of the upper metallic mold abuts against the surface of the semiconductor element when the upper metallic mold is placed on the wiring substrate, and the metal wire is thereby protected.
Moreover, in the second aspect of the present invention, the protruding portion provided inside of the upper metallic mold is preferably formed at a position corresponding to a boundary between the plurality of semiconductor devices in such a manner that the height of the protruding portion is substantially equal to that of the mold resin formed on the semiconductor element. As a result, even if the wiring substrate warps, the protruding portion of the upper metallic mold abuts against the wiring substrate at a position corresponding to the boundary between the semiconductor devices with the upper metallic mold placed on the wiring substrate. Accordingly, warp of the wiring substrate is suppressed and the metal wire is thereby protected.
According to the third aspect of the present invention, the contact prevention resin having a predetermined height is fixed to the surface of each of the semiconductor elements. As a result, when mold processing is carried out in which the semiconductor elements are mounted all together on the wiring substrate, even if the wiring substrate warps, the inner surface of the upper metal mold placed on the wiring substrate abuts against the contact prevention resin and the metal wire is thereby protected. Accordingly, there is reduced risk of deforming the metal wire.